As previously mentioned, media elements must either be converted to a digital format or derive from a digital source in order to be used on the computer. Visual images—such as photos, drawings, and paintings—must be digitized, either by scanning with a flatbed scanner or photographing with a digital camera. Photographic images can also be acquired digitally in their original form by using a digital camera from the start. Either way, they will end up in a computer- friendly format that can be included in a multimedia presentation. Video and audio are similar in that they need to be converted using analog-to-digital technology or captured using a digital video camera in its native format.
The term analog generally refers to traditional, physical media, such as video and cassette tapes. This technology was used before the advent of computers that transmitted continuous TV and radio signals resulting in a linear representation. Videotapes were originally developed as a means of recording and playing back analog signals transmitted wirelessly or by cable. Later, they were designed for the home market to record live action for family movies. These days, most video is shot using a portable digital video camera so that the need to use an analog-to-digital converter is eliminated. This process saves steps and is also preferred when producing multimedia, as the screen dimensions and file size requirements are typically small and do not require high-end equipment.
A photograph that derives from a film negative and is printed on light-sensitive paper in a darkroom (or commercially printed) is also an analog source. Music recorded onto vinyl records and movies produced on celluloid filmstrips are other examples.
The analog-to-digital evolution is still occurring as we speak, but much of what is used for multimedia today is digital to begin with. This makes the development of a project easier and quicker, and ultimately cheaper to produce. The arrival of digital cameras in the early 1990s, for instance, allowed photographers to generate average-quality digital images. Over time, lower costs and improvements in technology have spawned numerous brands and models of digital still cameras, and now higher-quality results are commonplace and expected. In the early days, relatively affordable cameras were very limited. They had a maximum resolution of 72 pixels per inch. The dimensions were limited to 640-by-480 (equal to 6-by-8 inches, or the average dimensions of a 13-inch computer monitor, which was standard at the time), with a 256-color palette, and the image yielded a 900KB file. Average photos taken with a digital camera today are at least 9MB, sporting millions of colors, which is ten times as large with a much higher-quality result.
When scanning or digitizing photographic images for multimedia, the end product and file size are very important. In other words, your goal is to have the highest quality image or sound file possible, but one that is also small enough to play seamlessly on a multimedia CD or the Web. Another factor in the quality of digital media is that it is dependent on the equipment and technique used to acquire or convert it. A multimedia developer must establish in advance what the delivery format will be, as this will determine how the media files will be treated and prepared. More in-depth information on this topic will be discussed later in the book.
